Electrically variable transmission having three interconnected planetary gear sets

ABSTRACT

The electrically variable transmission family of the present invention provides low-content, low-cost electrically variable transmission mechanisms including first, second and third differential gear sets, a battery, two electric machines serving interchangeably as motors or generators, and four or five selectable torque-transfer devices (two clutches and two or three brakes). The four or five selectable torque transfer devices are engaged singly or in combinations of two to yield an EVT with a continuously variable range of speeds (including reverse) and four mechanically fixed forward speed ratios. The torque transfer devices and the first and second motor/generators are operable to provide five operating modes in the electrically variable transmission, including battery reverse mode, EVT reverse mode, reverse and forward launch modes, continuously variable transmission range mode, and fixed ratio mode.

TECHNICAL FIELD

The present invention relates to electrically variable transmissionswith selective operation both in power-split variable speed ratio rangesand in fixed speed ratios, and having three planetary gear sets, twomotor/generators and four or five torque transfer devices.

BACKGROUND OF THE INVENTION

Internal combustion engines, particularly those of the reciprocatingpiston type, currently propel most vehicles. Such engines are relativelyefficient, compact, lightweight, and inexpensive mechanisms by which toconvert highly concentrated energy in the form of fuel into usefulmechanical power. A novel transmission system, which can be used withinternal combustion engines and which can reduce fuel consumption andthe emissions of pollutants, may be of great benefit to the public.

The wide variation in the demands that vehicles typically place oninternal combustion engines increases fuel consumption and emissionsbeyond the ideal case for such engines. Typically, a vehicle ispropelled by such an engine, which is started from a cold state by asmall electric motor and relatively small electric storage batteries,then quickly placed under the loads from propulsion and accessoryequipment. Such an engine is also operated through a wide range ofspeeds and a wide range of loads and typically at an average ofapproximately a fifth of its maximum power output.

A vehicle transmission typically delivers mechanical power from anengine to the remainder of a drive system, such as fixed final drivegearing, axles and wheels. A typical mechanical transmission allows somefreedom in engine operation, usually through alternate selection of fiveor six different drive ratios, a neutral selection that allows theengine to operate accessories with the vehicle stationary, and clutchesor a torque converter for smooth transitions between driving ratios andto start the vehicle from rest with the engine turning. Transmissiongear selection typically allows power from the engine to be delivered tothe rest of the drive system with a ratio of torque multiplication andspeed reduction, with a ratio of torque reduction and speedmultiplication known as overdrive, or with a reverse ratio.

An electric generator can transform mechanical power from the engineinto electrical power, and an electric motor can transform that electricpower back into mechanical power at different torques and speeds for theremainder of the vehicle drive system. This arrangement allows acontinuous variation in the ratio of torque and speed between engine andthe remainder of the drive system, within the limits of the electricmachinery. An electric storage battery used as a source of power forpropulsion may be added to this arrangement, forming a series hybridelectric drive system.

The series hybrid system allows the engine to operate with someindependence from the torque, speed and power required to propel avehicle, so the engine may be controlled for improved emissions andefficiency. This system allows the electric machine attached to theengine to act as a motor to start the engine. This system also allowsthe electric machine attached to the remainder of the drive train to actas a generator, recovering energy from slowing the vehicle into thebattery by regenerative braking. A series electric drive suffers fromthe weight and cost of sufficient electric machinery to transform all ofthe engine power from mechanical to electrical in the generator and fromelectrical to mechanical in the drive motor, and from the useful energylost in these conversions.

A power-split transmission can use what is commonly understood to be“differential gearing” to achieve a continuously variable torque andspeed ratio between input and output. An electrically variabletransmission can use differential gearing to send a fraction of itstransmitted power through a pair of electric motor/generators. Theremainder of its power flows through another, parallel path that is allmechanical and direct, of fixed ratio, or alternatively selectable.

One form of differential gearing, as is well known to those skilled inthis art, may constitute a planetary gear set. Planetary gearing isusually the preferred embodiment employed in differentially gearedinventions, with the advantages of compactness and different torque andspeed ratios among all members of the planetary gear set. However, it ispossible to construct this invention without planetary gears, as byusing bevel gears or other gears in an arrangement where the rotationalspeed of at least one element of a gear set is always a weighted averageof speeds of two other elements.

A hybrid electric vehicle transmission system also includes one or moreelectric energy storage devices. The typical device is a chemicalelectric storage battery, but capacitive or mechanical devices, such asan electrically driven flywheel, may also be included. Electric energystorage allows the mechanical output power from the transmission systemto the vehicle to vary from the mechanical input power from the engineto the transmission system. The battery or other device also allows forengine starting with the transmission system and for regenerativevehicle braking.

An electrically variable transmission in a vehicle can simply transmitmechanical power from an engine input to a final drive output. To do so,the electric power produced by one motor/generator balances theelectrical losses and the electric power consumed by the othermotor/generator. By using the above-referenced electrical storagebattery, the electric power generated by one motor/generator can begreater than or less than the electric power consumed by the other.Electric power from the battery can sometimes allow bothmotor/generators to act as motors, especially to assist the engine withvehicle acceleration. Both motors can sometimes act as generators torecharge the battery, especially in regenerative vehicle braking.

A successful substitute for the series hybrid transmission is thetwo-range, input-split and compound-split electrically variabletransmission now produced for transit buses, as disclosed in U.S. Pat.No. 5,931,757, issued Aug. 3, 1999, to Michael Roland Schmidt, commonlyassigned with the present application, and hereby incorporated byreference in its entirety. Such a transmission utilizes an input meansto receive power from the vehicle engine and a power output means todeliver power to drive the vehicle. First and second motor/generatorsare connected to an energy storage device, such as a battery, so thatthe energy storage device can accept power from, and supply power to,the first and second motor/generators. A control unit regulates powerflow among the energy storage device and the motor/generators as well asbetween the first and second motor/generators.

Operation in first or second variable-speed-ratio modes of operation maybe selectively achieved by using clutches in the nature of first andsecond torque transfer devices. In the first mode, an input-power-splitspeed ratio range is formed by the application of the first clutch, andthe output speed of the transmission is proportional to the speed of onemotor/generator. In the second mode, a compound-power-split speed ratiorange is formed by the application of the second clutch, and the outputspeed of the transmission is not proportional to the speeds of either ofthe motor/generators, but is an algebraic linear combination of thespeeds of the two motor/generators. Operation at a fixed transmissionspeed ratio may be selectively achieved by the application of both ofthe clutches. Operation of the transmission in a neutral mode may beselectively achieved by releasing both clutches, decoupling the engineand both electric motor/generators from the transmission output. Thetransmission incorporates at least one mechanical point in its firstmode of operation and at least two mechanical points in its second modeof operation.

U.S. Pat. No. 6,527,658, issued Mar. 4, 2003 to Holmes et al, commonlyassigned with the present application, and hereby incorporated byreference in its entirety, discloses an electrically variabletransmission utilizing two planetary gear sets, two motor/generators andtwo clutches to provide input split, compound split, neutral and reversemodes of operation. Both planetary gear sets may be simple, or one maybe individually compounded. An electrical control member regulates powerflow among an energy storage device and the two motor/generators. Thistransmission provides two ranges or modes of electrically variabletransmission (EVT) operation, selectively providing an input-power-splitspeed ratio range and a compound-power-split speed ratio range. Onefixed speed ratio can also be selectively achieved.

SUMMARY OF THE INVENTION

The present invention provides a family of electrically variabletransmissions offering several advantages over conventional automatictransmissions for use in hybrid vehicles, including improved vehicleacceleration performance, improved fuel economy via regenerative brakingand electric-only idling and launch, and an attractive marketingfeature. An object of the invention is to provide the best possibleenergy efficiency and emissions for a given engine. In addition, optimalperformance, capacity, package size, and ratio coverage for thetransmission are sought.

The electrically variable transmission family of the present inventionprovides low-content, low-cost electrically variable transmissionmechanisms including first, second and third differential gear sets, abattery, two electric machines serving interchangeably as motors orgenerators, and four or five selectable torque-transfer devices (twoclutches and two or three brakes). Preferably, the differential gearsets are planetary gear sets, but other gear arrangements may beimplemented, such as bevel gears or differential gearing to an offsetaxis.

In this description, the first, second, or third planetary gear sets maybe counted first to third in any order (i.e., left to right, right toleft, etc.).

Each of the three planetary gear sets has three members. The first,second or third member of each planetary gear set can be any one of asun gear, ring gear or carrier.

Each carrier can be either a single-pinion carrier (simple) or adouble-pinion carrier (compound).

The input shaft is continuously connected with at least one member ofthe planetary gear sets. The output shaft is continuously connected withanother member of the planetary gear sets.

A first interconnecting member continuously connects a first member ofthe first planetary gear set and a first member of the second planetarygear set.

A second interconnecting member continuously connects a second member ofthe first planetary gear set with a second member of the secondplanetary gear set and with a second member of the third planetary gearset.

A first torque transfer device selectively connects a member of thefirst or second planetary gear set with another member of the first orthird planetary gear set.

A second torque transfer device selectively connects a member of thethird planetary gear set with another member of the first, second orthird planetary gear set, this pair of members being different from theones connected by the first torque transfer device.

A third torque transfer device selectively connects a member of thesecond or third planetary gear set with a stationary member(transmission case).

A fourth torque transfer device is connected in parallel with one of themotor/generators for selectively preventing rotation of themotor/generator.

An optional fifth torque transfer device may be connected in parallelwith the other motor/generator for selectively preventing rotationthereof.

The first motor/generator is mounted to the transmission case (orground) and is continuously connected to the first interconnectingmember.

The second motor/generator is mounted to the transmission case and iscontinuously connected to a member of the second or third planetary gearset.

The four or five selectable torque transfer devices (two clutches andtwo or three brakes) are engaged singly or in combinations of two toyield an EVT with a continuously variable range of speeds (includingreverse) and four mechanically fixed forward speed ratios. A “fixedspeed ratio” is an operating condition in which the mechanical powerinput to the transmission is transmitted mechanically to the output, andno power flow (i.e. almost zero) is present in the motor/generators. Anelectrically variable transmission that may selectively achieve severalfixed speed ratios for operation near full engine power can be smallerand lighter for a given maximum capacity. Fixed ratio operation may alsoresult in lower fuel consumption when operating under conditions whereengine speed can approach its optimum without using themotor/generators. A variety of fixed speed ratios and variable ratiospreads can be realized by suitably selecting the tooth ratios of theplanetary gear sets.

Each embodiment of the electrically variable transmission familydisclosed has an architecture in which neither the transmission inputnor output is directly connected to a motor/generator. This allows for areduction in the size and cost of the electric motor/generators requiredto achieve the desired vehicle performance.

The first, second, third and fourth (and perhaps fifth) torque transferdevices, motor brake(s), and the first and second motor/generators areoperable to provide five operating modes in the electrically variabletransmission, including battery reverse mode, EVT reverse mode, reverseand forward launch modes, continuously variable transmission range mode,and fixed ratio mode.

The above features and advantages, and other features and advantages ofthe present invention are readily apparent from the following detaileddescription of the best modes for carrying out the invention when takenin connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 a is a schematic representation of a powertrain including anelectrically variable transmission incorporating a family member of thepresent invention;

FIG. 1 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 1a;

FIG. 2 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 2 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 2a;

FIG. 3 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 3 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 3a;

FIG. 4 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 4 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 4a;

FIG. 5 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 5 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 5a;

FIG. 6 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 6 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 6a;

FIG. 7 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention;

FIG. 7 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 7a;

FIG. 8 a is a schematic representation of a powertrain having anelectrically variable transmission incorporating another family memberof the present invention; and

FIG. 8 b is an operating mode table and fixed ratio mode table depictingsome of the operating characteristics of the powertrain shown in FIG. 8a.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

With reference to FIG. 1 a, a powertrain 10 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission (EVT), designated generally by thenumeral 14. Transmission 14 is designed to receive at least a portion ofits driving power from the engine 12. As shown, the engine 12 has anoutput shaft that serves as the input member 17 of the transmission 14.A transient torque damper (not shown) may also be implemented betweenthe engine 12 and the input member 17 of the transmission.

In the embodiment depicted the engine 12 may be a fossil fuel engine,such as a diesel engine which is readily adapted to provide itsavailable power output typically delivered at a constant number ofrevolutions per minute (RPM).

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set 20 in the transmission 14.

An output member 19 of the transmission 14 is connected to a final drive16.

The transmission 14 utilizes three differential gear sets, preferably inthe nature of planetary gear sets 20, 30 and 40. The planetary gear set20 employs an outer gear member 24, typically designated as the ringgear. The ring gear 24 circumscribes an inner gear member 22, typicallydesignated as the sun gear. A carrier 26 rotatably supports a pluralityof planet gears 27 such that each planet gear 27 meshingly engages boththe outer, ring gear member 24 and the inner, sun gear member 22 of thefirst planetary gear set 20. The input member 17 is secured to the ringgear member 24 of the planetary gear set 20.

The planetary gear set 30 also has an outer gear member 34, often alsodesignated as the ring gear, that circumscribes an inner gear member 32,also often designated as the sun gear. A plurality of planet gears 37are also rotatably mounted in a carrier 36 such that each planet gearmember 37 simultaneously, and meshingly, engages both the outer, ringgear member 34 and the inner, sun gear member 32 of the planetary gearset 30.

The planetary gear set 40 also has an outer gear member 44, often alsodesignated as the ring gear, that circumscribes an inner gear member 42,also often designated as the sun gear. A plurality of planet gears 47are also rotatably mounted in a carrier 46 such that each planet gearmember 47 simultaneously, and meshingly, engages both the outer, ringgear member 44 and the inner, sun gear member 42 of the planetary gearset 40.

A first interconnecting member 70 continuously connects the carrier 26of the planetary gear set 20 with the carrier 36 of the planetary gearset 30. A second interconnecting member 72 continuously connects the sungear 22 of the planetary gear set 20 with the ring gear 34 of theplanetary gear set 30 and with the sun gear 42 of the planetary gear set40. The second interconnecting member 72 may be a one piece or two piececomponent.

The first preferred embodiment 10 also incorporates first and secondmotor/generators 80 and 82, respectively. The stator of the firstmotor/generator 80 is secured to the transmission housing 60. The rotorof the first motor/generator 80 is secured to the first interconnectingmember 70.

The stator of the second motor/generator 82 is also secured to thetransmission housing 60. The rotor of the second motor/generator 82 issecured to the sun gear 32.

A first torque transfer device, such as a clutch 50, selectivelyconnects the ring gear 24 of the planetary gear set 20 to the sun gear22 of the planetary gear set 20. A second torque transfer device, suchas clutch 52, selectively connects the sun gear 32 of the planetary gearset 30 with the ring gear 44 of the planetary gear set 40. A thirdtorque transfer device, such as brake 54, selectively connects the ringgear 44 of the planetary gear set 40 with the transmission housing 60.That is, the ring gear 44 is selectively secured against rotation by anoperative connection to the non-rotatable housing 60. A fourth torquetransfer device 55 is connected in parallel with the motor/generator 80for selectively braking rotation of the motor/generator 80. A fifthtorque transfer device 57 is connected in parallel with themotor/generator 82 for selectively braking rotation of themotor/generator 82. Engagement of the brakes 55, 57 is indicated by an“X” in the column of the respective motor/generator in the chart of FIG.1 b. The first, second, third, fourth and fifth torque transfer devices50, 52, 54, 55 and 57 are employed to assist in the selection of theoperational modes of the hybrid transmission 14, as will be hereinaftermore fully explained.

The output drive member 19 of the transmission 14 is secured to thecarrier 46 of the planetary gear set 40.

Returning now to the description of the power sources, it should beapparent from the foregoing description, and with particular referenceto FIG. 1 a, that the transmission 14 selectively receives power fromthe engine 12. The hybrid transmission also receives power from anelectric power source 86, which is operably connected to a controller88. The electric power source 86 may be one or more batteries. Otherelectric power sources, such as fuel cells, that have the ability toprovide, or store, and dispense electric power may be used in place ofbatteries without altering the concepts of the present invention.

General Operating Considerations

One of the primary control devices is a well known drive range selector(not shown) that directs an electronic control unit (the ECU 88) toconfigure the transmission for either the park, reverse, neutral, orforward drive range. The second and third primary control devicesconstitute an accelerator pedal (not shown) and a brake pedal (also notshown). The information obtained by the ECU from these three primarycontrol sources is designated as the “operator demand.” The ECU alsoobtains information from a plurality of sensors (input as well asoutput) as to the status of: the torque transfer devices (either appliedor released); the engine output torque; the unified battery, orbatteries, capacity level; and, the temperatures of selected vehicularcomponents. The ECU determines what is required and then manipulates theselectively operated components of, or associated with, the transmissionappropriately to respond to the operator demand.

The invention may use simple or compound planetary gear sets. In asimple planetary gear set a single set of planet gears are normallysupported for rotation on a carrier that is itself rotatable.

In a simple planetary gear set, when the sun gear is held stationary andpower is applied to the ring gear of a simple planetary gear set, theplanet gears rotate in response to the power applied to the ring gearand thus “walk” circumferentially about the fixed sun gear to effectrotation of the carrier in the same direction as the direction in whichthe ring gear is being rotated.

When any two members of a simple planetary gear set rotate in the samedirection and at the same speed, the third member is forced to turn atthe same speed, and in the same direction. For example, when the sungear and the ring gear rotate in the same direction, and at the samespeed, the planet gears do not rotate about their own axes but ratheract as wedges to lock the entire unit together to effect what is knownas direct drive. That is, the carrier rotates with the sun and ringgears.

However, when the two gear members rotate in the same direction, but atdifferent speeds, the direction in which the third gear member rotatesmay often be determined simply by visual analysis, but in manysituations the direction will not be obvious and can only be accuratelydetermined by knowing the number of teeth present on all the gearmembers of the planetary gear set.

Whenever the carrier is restrained from spinning freely, and power isapplied to either the sun gear or the ring gear, the planet gear membersact as idlers. In that way the driven member is rotated in the oppositedirection as the drive member. Thus, in many transmission arrangementswhen the reverse drive range is selected, a torque transfer deviceserving as a brake is actuated frictionally to engage the carrier andthereby restrain it against rotation so that power applied to the sungear will turn the ring gear in the opposite direction. Thus, if thering gear is operatively connected to the drive wheels of a vehicle,such an arrangement is capable of reversing the rotational direction ofthe drive wheels, and thereby reversing the direction of the vehicleitself.

In a simple set of planetary gears, if any two rotational speeds of thesun gear, the planet carrier, and the ring gear are known, then thespeed of the third member can be determined using a simple rule. Therotational speed of the carrier is always proportional to the speeds ofthe sun and the ring, weighted by their respective numbers of teeth. Forexample, a ring gear may have twice as many teeth as the sun gear in thesame set. The speed of the carrier is then the sum of two-thirds thespeed of the ring gear and one-third the speed of the sun gear. If oneof these three members rotates in an opposite direction, the arithmeticsign is negative for the speed of that member in mathematicalcalculations.

The torque on the sun gear, the carrier, and the ring gear can also besimply related to one another if this is done without consideration ofthe masses of the gears, the acceleration of the gears, or frictionwithin the gear set, all of which have a relatively minor influence in awell designed transmission. The torque applied to the sun gear of asimple planetary gear set must balance the torque applied to the ringgear, in proportion to the number of teeth on each of these gears. Forexample, the torque applied to a ring gear with twice as many teeth asthe sun gear in that set must be twice that applied to the sun gear, andmust be applied in the same direction. The torque applied to the carriermust be equal in magnitude and opposite in direction to the sum of thetorque on the sun gear and the torque on the ring gear.

In a compound planetary gear set, the utilization of inner and outersets of planet gears effects an exchange in the roles of the ring gearand the planet carrier in comparison to a simple planetary gear set. Forinstance, if the sun gear is held stationary, the planet carrier willrotate in the same direction as the ring gear, but the planet carrierwith inner and outer sets of planet gears will travel faster than thering gear, rather than slower.

In a compound planetary gear set having meshing inner and outer sets ofplanet gears the speed of the ring gear is proportional to the speeds ofthe sun gear and the planet carrier, weighted by the number of teeth onthe sun gear and the number of teeth filled by the planet gears,respectively. For example, the difference between the ring and the sunfilled by the planet gears might be as many teeth as are on the sun gearin the same set. In that situation the speed of the ring gear would bethe sum of two-thirds the speed of the carrier and one third the speedof the sun. If the sun gear or the planet carrier rotates in an oppositedirection, the arithmetic sign is negative for that speed inmathematical calculations.

If the sun gear were to be held stationary, then a carrier with innerand outer sets of planet gears will turn in the same direction as therotating ring gear of that set. On the other hand, if the sun gear wereto be held stationary and the carrier were to be driven, then planetgears in the inner set that engage the sun gear roll, or “walk,” alongthe sun gear, turning in the same direction that the carrier isrotating. Pinion gears in the outer set that mesh with pinion gears inthe inner set will turn in the opposite direction, thus forcing ameshing ring gear in the opposite direction, but only with respect tothe planet gears with which the ring gear is meshingly engaged. Theplanet gears in the outer set are being carried along in the directionof the carrier. The effect of the rotation of the pinion gears in theouter set on their own axis and the greater effect of the orbital motionof the planet gears in the outer set due to the motion of the carrierare combined, so the ring rotates in the same direction as the carrier,but not as fast as the carrier.

If the carrier in such a compound planetary gear set were to be heldstationary and the sun gear were to be rotated, then the ring gear willrotate with less speed and in the same direction as the sun gear. If thering gear of a simple planetary gear set is held stationary and the sungear is rotated, then the carrier supporting a single set of planetgears will rotate with less speed and in the same direction as the sungear. Thus, one can readily observe the exchange in roles between thecarrier and the ring gear that is caused by the use of inner and outersets of planet gears which mesh with one another, in comparison with theusage of a single set of planet gears in a simple planetary gear set.

The normal action of an electrically variable transmission is totransmit mechanical power from the input to the output. As part of thistransmission action, one of its two motor/generators acts as a generatorof electrical power. The other motor/generator acts as a motor and usesthat electrical power. As the speed of the output increases from zero toa high speed, the two motor/generators 80, 82 gradually exchange rolesas generator and motor, and may do so more than once. These exchangestake place around mechanical points, where essentially all of the powerfrom input to output is transmitted mechanically and no substantialpower is transmitted electrically.

In a hybrid electrically variable transmission system, the battery 86may also supply power to the transmission or the transmission may supplypower to the battery. If the battery is supplying substantial electricpower to the transmission, such as for vehicle acceleration, then bothmotor/generators may act as motors. If the transmission is supplyingelectric power to the battery, such as for regenerative braking, bothmotor/generators may act as generators. Very near the mechanical pointsof operation, both motor/generators may also act as generators withsmall electrical power outputs, because of the electrical losses in thesystem.

Contrary to the normal action of the transmission, the transmission mayactually be used to transmit mechanical power from the output to theinput. This may be done in a vehicle to supplement the vehicle brakesand to enhance or to supplement regenerative braking of the vehicle,especially on long downward grades. If the power flow through thetransmission is reversed in this way, the roles of the motor/generatorswill then be reversed from those in normal action.

Specific Operating Considerations

Each of the embodiments described herein has sixteen functionalrequirements (corresponding with the 16 rows of each operating modetable shown in the Figures) which may be grouped into five operatingmodes. These five operating modes are described below and may be bestunderstood by referring to the respective operating mode tableaccompanying each transmission stick diagram, such as the operating modetables of FIG. 1 b, 2 b, 3 b, etc.

The first operating mode is the “battery reverse mode” which correspondswith the first row (Batt Rev) of each operating mode table, such as thatof FIG. 1 b. In this mode, the engine is off and the transmissionelement connected to the engine is not controlled by engine torque,though there may be some residual torque due to the rotational inertiaof the engine. The EVT is driven by one of the motor/generators usingenergy from the battery, causing the vehicle to move in reverse.Depending on the kinematic configuration, the other/motor/generator mayor may not rotate in this mode, and may or may not transmit torque. Ifit does rotate, it is used to generate energy which is stored in thebattery. In the embodiment of FIG. 1 b, in the battery reverse mode, thebrakes 54 and 55 are engaged, and the motor 82 has a torque of 0.29units. A torque ratio of −7.50 is achieved, by way of example. In eachoperating mode table an (M) next to a torque value in themotor/generator columns 80 and 82 indicates that the motor/generator isacting as a motor, and the absence of an (M) indicates that themotor/generator is acting as generator; also, an “X” indicates that therespective brake 55, 57 is engaged.

The second operating mode is the “EVT reverse mode” (or hybrid reversemode) which corresponds with the second row (EVT Rev) of each operatingmode table, such as that of FIG. 1 b. In this mode, the EVT is driven bythe engine and by one of the motor/generators. The other motor/generatoroperates in generator mode and transfers 100% of the generated energyback to the driving motor. The net effect is to drive the vehicle inreverse. Referring to FIG. 1 b, for example, in the EVT reverse mode,the brake 54 is engaged, the generator 80 has a torque of −4.59 units,the motor 82 has a torque of 0.74 units, and an output torque of −8.34is achieved, corresponding to an engine torque of 1 unit.

The third operating mode includes the “reverse and forward launch modes”(also referred to as “torque converter reverse and forward modes”)corresponding with the third and fourth rows (TC Rev and TC For) of eachoperating mode table, such as that of FIG. 1 b. In this mode, the EVT isdriven by the engine and one of the motor/generators. A selectablefraction of the energy generated in the generator unit is stored in thebattery, with the remaining energy being transferred to the motor. InFIG. 1, this fraction is approximately 99%. The ratio of transmissionoutput speed to engine speed (transmission speed ratio) is approximately+/−0.001 (the positive sign indicates that the vehicle is creepingforward and negative sign indicates that the vehicle is creepingbackwards). Referring to FIG. 1 b, in the reverse launch mode, the brake54 is engaged, and the motor/generator 80 acts as a generator with −3.97units of torque, the motor/generator 82 acts as a motor with 0.59 unitsof torque, and a torque ratio of −7.00 is achieved. In the forwardlaunch mode, the brake 54 is engaged, and the motor/generator 80 acts asa motor with 1.37 units of torque, the motor/generator 82 acts as agenerator with −0.77 units of torque, and a torque ratio of 4.69 isachieved.

The fourth operating mode is a “continuously variable transmission rangemode” which includes the Range 1.1, Range 1.2, Range 1.3, Range 1.4,Range 2.1, Range 2.2, Range 2.3 and Range 2.4 operating pointscorresponding with rows 5–12 of each operating point table, such as thatof FIG. 1 b. In this mode, the EVT is driven by the engine as well asone of the motor/generators operating as a motor. The othermotor/generator operates as a generator and transfers 100% of thegenerated energy back to the motor. The operating points represented byRange 1.1, 1.2 . . . , etc. are discrete points in the continuum offorward speed ratios provided by the EVT. For example in FIG. 1 b, arange of torque ratios from 4.69 to 1.86 is achieved with the brake 54engaged, and a range of ratios 1.36 to 0.54 is achieved with the clutch52 engaged.

The fifth operating mode includes the “fixed ratio” modes (F1, F2, F3and F4) corresponding with rows 13–16 of each operating mode table (i.e.operating mode table), such as that of FIG. 1 b. In this mode thetransmission operates like a conventional automatic transmission, withtwo torque transfer devices engaged to create a discrete transmissionratio, or one torque-transfer device may be engaged while onemotor/generator is braked. Alternatively, all three torque transferdevices could be disengaged while both motor/generators are braked. Theclutching table accompanying each figure shows only 4 fixed-ratioforward speeds but additional fixed ratios may be available. Referringto FIG. 1 b, in fixed ratio F1 the clutch 50 and brake 54 are engaged toachieve a fixed torque ratio of 2.93. In fixed ratio F2, the brakes 54,57 are engaged to achieve a fixed ratio of 1.69. Accordingly, each “X”in the column of motor/generator 82 in FIG. 1 b indicates that the brake57 is engaged and the motor/generator 82 is not rotating. In fixed ratioF3, the clutches 50 and 52 are engaged to achieve a fixed ratio of 1.00.In fixed ratio F4, the clutch 52 is engaged and the motor/generator 80is braked by the brake 55 to achieve a fixed ratio of 0.42.

The transmission 14 is capable of operating in so-called single or dualmodes. In single mode, the engaged torque transfer device remains thesame for the entire continuum of forward speed ratios (represented bythe discrete points: Ranges 1.1, 1.2, 1.3 and 1.4). In dual mode, theengaged torque transfer device is switched at some intermediate speedratio (e.g., Range 2.1 in FIG. 1). Depending on the mechanicalconfiguration, this change in torque transfer device engagement hasadvantages in reducing element speeds in the transmission.

In some designs, it is possible to synchronize clutch element slipspeeds such that shifts are achievable with minimal torque disturbance(so-called “cold” shifts). For example, the transmission of FIG. 1 a hasa cold shift between ranges 1.4 and 2.1. This also serves as an enablerfor superior control during double transition shifts (two oncomingclutches and two off-going clutches).

As set forth above, the engagement schedule for the torque transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 1 b. FIG. 1 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 1 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 20; the N_(R2)/N_(S2) value is the tooth ratio of theplanetary gear set 30; and the N_(R3)/N_(S3) value is the tooth ratio ofthe planetary gear set 40. Also, the chart of FIG. 1 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 1.73, the step ratio between the second andthird fixed forward torque ratios is 1.69, the step ratio between thesecond and third fixed forward torque ratios is 2.38, and the ratiospread is 4.73.

Description of a Second Exemplary Embodiment

With reference to FIG. 2 a, a powertrain 110 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral114. Transmission 114 is designed to receive at least a portion of itsdriving power from the engine 12.

In the embodiment depicted the engine 12 may also be a fossil fuelengine, such as a diesel engine which is readily adapted to provide itsavailable power output typically delivered at a constant number ofrevolutions per minute (RPM). As shown, the engine 12 has an outputshaft that serves as the input member 17 of the transmission 14. Atransient torque damper (not shown) may also be implemented between theengine 12 and the input member 17 of the transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 114.An output member 19 of the transmission 114 is connected to a finaldrive 16.

The transmission 114 utilizes three differential gear sets, preferablyin the nature of planetary gear sets 120, 130 and 140. The planetarygear set 120 employs an outer gear member 124, typically designated asthe ring gear. The ring gear 124 circumscribes an inner gear member 122,typically designated as the sun gear. A carrier 126 rotatably supports aplurality of planet gears 127 such that each planet gear 127 meshinglyengages both the outer, ring gear member 124 and the inner, sun gearmember 122 of the first planetary gear set 120.

The planetary gear set 130 also has an outer gear member 134, often alsodesignated as the ring gear, that circumscribes an inner gear member132, also often designated as the sun gear. A plurality of planet gears137 are also rotatably mounted in a carrier 136 such that each planetgear member 137 simultaneously, and meshingly, engages both the outer,ring gear member 134 and the inner, sun gear member 132 of the planetarygear set 130.

The planetary gear set 140 also has an outer gear member 144, often alsodesignated as the ring gear, that circumscribes an inner gear member142, also often designated as the sun gear. A plurality of planet gears147 are also rotatably mounted in a carrier 146 such that each planetgear member 147 simultaneously, and meshingly, engages both the outer,ring gear member 144 and the inner, sun gear member 142 of the planetarygear set 140.

The transmission input member 17 is connected with the carrier 126 ofthe planetary gear set 120, and the transmission output member 19 isconnected with the carrier 146 of the planetary gear set 140. A firstinterconnecting member 170 continuously connects the sun gear 122 of theplanetary gear set 120 with the sun gear 132 of the planetary gear set130. A second interconnecting member 172 continuously connects the ringgear 124 of the planetary gear set 120 with the carrier 136 of theplanetary gear set 130, and with the ring gear 144 of the planetary gearset 140.

The transmission 114 also incorporates first and second motor/generators180 and 182, respectively. The stator of the first motor/generator 180is secured to the transmission housing 160. The rotor of the firstmotor/generator 180 is secured to the sun gear 122 of the planetary gearset 120.

The stator of the second motor/generator 182 is also secured to thetransmission housing 160. The rotor of the second motor/generator 182 issecured to the sun gear 142.

A first torque transfer device, such as a clutch 150, selectivelyconnects the carrier 126 of the planetary gear set 120 to the sun gear122 of the planetary gear set 120. A second torque transfer device, suchas clutch 152, selectively connects the ring gear 134 of the planetarygear set 130 with the carrier 146 of the planetary gear set 140. A thirdtorque transfer device, such as brake 154, selectively connects the ringgear 134 of the planetary gear set 130 with the transmission housing160. That is, the ring gear 134 is selectively secured against rotationby an operative connection to the non-rotatable housing 160. A fourthtorque transfer device, such as the brake 155, is connected in parallelwith the motor/generator 180 for selectively braking rotation of themotor/generator 180. A fifth torque transfer device, such as the brake157, is connected in parallel with the motor/generator 182 forselectively braking rotation of the motor/generator 182. The first,second, third, fourth and fifth torque transfer devices 150, 152, 154,155 and 157 are employed to assist in the selection of the operationalmodes of the hybrid transmission 14.

Returning now to the description of the power sources, it should beapparent from the foregoing description, and with particular referenceto FIG. 2 a, that the transmission 114 selectively receives power fromthe engine 12. The hybrid transmission also exchanges power with anelectric power source 186, which is operably connected to a controller188. The electric power source 186 may be one or more batteries. Otherelectric power sources, such as fuel cells, that have the ability toprovide, or store, and dispense electric power may be used in place ofbatteries without altering the concepts of the present invention.

As described previously, each embodiment has sixteen functionalrequirements (corresponding with the 16 rows of each operating modetable shown in the Figures) which may be grouped into five operatingmodes. The first operating mode is the “battery reverse mode” whichcorresponds with the first row (Batt Rev) of the operating mode table ofFIG. 2 b. In this mode, the engine is off and the transmission elementconnected to the engine is effectively allowed to freewheel, subject toengine inertia torque. The EVT is driven by one of the motor/generatorsusing energy from the battery, causing the vehicle to move in reverse.The other motor/generator may or may not rotate in this mode. As shownin FIG. 2 b, in this mode, the brakes 152 and 157 are engaged, the motor180 has a torque of −0.29 units, the motor/generator 182 is braked, andan output torque of −3.67 is achieved, corresponding to an input torqueof 1 unit.

The second operating mode is the “EVT reverse mode” (or hybrid reversemode) which corresponds with the second row (EVT Rev) of the operatingmode table of FIG. 2 b. In this mode, the EVT is driven by the engineand by one of the motor/generators. The other motor/generator operatesin generator mode and transfers 100% of the generated energy back to thedriving motor. The net effect is to drive the vehicle in reverse. Inthis mode, the clutch 152 is engaged, the generator 180 has a torque of−0.83 units, the motor 182 has a torque of −1.85 units, and an outputtorque of −8.34 units is achieved, corresponding to an input torque of 1unit.

The third operating mode includes the “reverse and forward launch modes”corresponding with the third and fourth rows (TC Rev and TC For) of eachoperating mode table, such as that of FIG. 2 b. In this mode, the EVT isdriven by the engine and one of the motor/generators. A selectablefraction of the energy generated in the generator unit is stored in thebattery, with the remaining energy being transferred to the motor. Inthe TC Reverse mode, the clutch 152 is engaged, and the motor/generator180 acts as a generator with −0.72 units of torque, the motor/generator182 acts as a motor with −1.57 units of torque, and a torque ratio of−7.00 is achieved. In the TC Forward mode, the clutch 152 is engaged,and the motor/generator 180 acts as a motor with 0.51 units of torque,the motor/generator 182 acts as a generator with 2.33 units of torque,and a torque ratio of 4.69 is achieved. For these torque ratios,approximately 99% of the generator energy is stored in the battery.

The fourth operating mode includes the “Range 1.1, Range 1.2, Range 1.3,Range 1.4, Range 1.5, Range 1.6, Range 1.7 and Range 1.8” modescorresponding with rows 5–12 of the operating mode table of FIG. 2 b. Inthis mode, the EVT is driven by the engine as well as one of themotor/generators operating as a motor. The other motor/generatoroperates as a generator and transfers 100% of the generated energy backto the motor. The operating points represented by Range 1.1, 1.2 . . . ,etc. are discrete points in the continuum of forward speed ratiosprovided by the EVT. For example in FIG. 2 b, a range of ratios from4.69 to 0.54 is achieved with the clutch 152 engaged.

The fifth operating mode includes the fixed “ratio” modes (F1, F2, F3and F4) corresponding with rows 13–16 of the operating mode table ofFIG. 2 b. In this mode the transmission operates like a conventionalautomatic transmission, with two torque transfer devices engaged tocreate a discrete transmission ratio. In fixed ratio F1 the brakes 154,157 are engaged to achieve a fixed ratio of 3.16. In fixed ratio F2, theclutch 150 and brake 157 are engaged to achieve a fixed ratio of 1.67.In fixed ratio F3, the brakes 155 and 157 are engaged to achieve a fixedratio of 1.00. In fixed ratio F4, the clutch 152 and brake 155 areengaged to achieve a fixed ratio of 0.53.

As set forth above, the engagement schedule for the torque transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 2 b. FIG. 2 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 2 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 120; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 130; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 140. Also, the chart of FIG. 2 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.89, the step ratio between the secondand third fixed forward torque ratios is 1.43, and the step ratiobetween the third and fourth fixed forward torque ratios is 2.21.

Description of a Third Exemplary Embodiment

With reference to FIG. 3 a, a powertrain 210 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral214. The transmission 214 is designed to receive at least a portion ofits driving power from the engine 12. As shown, the engine 12 has anoutput shaft that serves as the input member 17 of the transmission 214.A transient torque damper (not shown) may also be implemented betweenthe engine 12 and the input member 17 of the transmission 214.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member isoperatively connected to a planetary gear set in the transmission 214.An output member 19 of the transmission 214 is connected to a finaldrive 16.

The transmission 214 utilizes three differential gear sets, preferablyin the nature of planetary gear sets 220, 230 and 240. The planetarygear set 220 employs an outer gear member 224, typically designated asthe ring gear. The ring gear 224 circumscribes an inner gear member 222,typically designated as the sun gear. A carrier 226 rotatably supports aplurality of planet gears 227 such that each planet gear 227 meshinglyengages both the outer, ring gear member 224 and the inner, sun gearmember 222 of the first planetary gear set 220.

The planetary gear set 230 also has an outer ring gear member 234 thatcircumscribes an inner sun gear member 232. A plurality of planet gears237 are also rotatably mounted in a carrier 236 such that each planetgear 237 simultaneously, and meshingly, engages both the outer ring gearmember 234 and the inner sun gear member 232 of the planetary gear set230.

The planetary gear set 240 also has an outer ring gear member 244 thatcircumscribes an inner sun gear member 242. A plurality of planet gears247 are rotatably mounted in a carrier 246 such that each planet gearmember 247 simultaneously and meshingly engages both the outer, ringgear member 244 and the inner, sun gear member 242 of the planetary gearset 240.

The transmission input member 17 is connected with the carrier 226, andthe transmission output member 19 is connected to the carrier 246. Afirst interconnecting member 270 continuously connects the sun gear 222of the planetary gear set 220 with the sun gear 232 of the planetarygear set 230. A second interconnecting member 272 connects the ring gear224 of the planetary gear set 220 with the carrier 236 of the planetarygear set 230, and with the ring gear 244 of the planetary gear set 240.

The transmission 214 also incorporates first and second motor/generators280 and 282, respectively. The stator of the first motor/generator 280is secured to the transmission housing 260. The rotor of the firstmotor/generator 280 is secured to the sun gear 222 of the planetary gearset 220.

The stator of the second motor/generator 282 is also secured to thetransmission housing 260. The rotor of the second motor/generator 282 issecured to the ring gear 234.

A first torque-transfer device, such as clutch 250, selectively connectsthe carrier 226 of the planetary gear set 220 with the sun gear 222 ofthe planetary gear set 220. A second torque-transfer device, such asclutch 252, selectively connects the ring gear 234 of the planetary gearset 230 with the sun gear 242 of the planetary gear set 240. A thirdtorque-transfer device, such as a brake 254, selectively connects thesun gear 242 of the planetary gear set 240 with the transmission housing260. A fourth torque transfer device, such as the brake 255, isconnected in parallel with the motor/generator 280 for selectivelybraking rotation of the motor/generator 280. A fifth torque transferdevice, such as the brake 257, is connected in parallel with themotor/generator 282 for selectively braking rotation of themotor/generator 282. The first, second, third, fourth and fifthtorque-transfer devices 250, 252, 254, 255 and 257 are employed toassist in the selection of the operational modes of the hybridtransmission 214.

The hybrid transmission 214 receives power from the engine 12, and alsofrom electric power source 286, which is operably connected to acontroller 288.

The operating mode table of FIG. 3 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 214. These modes include the“battery reverse mode” (Batt Rev), “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “range 1.1, 1.2,1.3 . . . modes” and “fixed ratio modes” (F1, F2, F3, F4) as describedpreviously.

As set forth above the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 3 b. FIG. 3 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 3 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 220; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 230; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 240. Also, the chart of FIG. 3 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between the first andsecond fixed forward torque ratios is 1.89, the step ratio between thesecond and third fixed forward torque ratios 1.43, and the step ratiobetween the third and fourth fixed forward torque ratios is 1.89.

Description of a Fourth Exemplary Embodiment

With reference to FIG. 4 a, a powertrain 310 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral314. The transmission 314 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 314. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 314.An output member 19 of the transmission 314 is connected to a finaldrive 16.

The transmission 314 utilizes three planetary gear sets 320, 330 and340. The planetary gear set 320 employs an outer ring gear member 324which circumscribes an inner sun gear member 322. A carrier 326rotatably supports a plurality of planet gears 327 such that each planetgear 327 meshingly engages both the outer ring gear member 324 and theinner sun gear member 322 of the first planetary gear set 320.

The planetary gear set 330 also has an outer ring gear member 334 thatcircumscribes an inner sun gear member 332. A plurality of planet gears337 are also rotatably mounted in a carrier 336 such that each planetgear member 337 simultaneously, and meshingly engages both the outer,ring gear member 334 and the inner, sun gear member 332 of the planetarygear set 330.

The planetary gear set 340 also has an outer ring gear member 344 thatcircumscribes an inner sun gear member 342. A plurality of planet gears347 are also rotatably mounted in a carrier 346 such that each planetgear member 347 simultaneously, and meshingly, engages both the outerring gear member 344 and the inner sun gear member 342 of the planetarygear set 340.

The transmission input member 17 is connected with the carrier 326 ofthe planetary gear set 320, and the transmission output member 19 isconnected with the carrier 346 of the planetary gear set 340. A firstinterconnecting member 370 continuously connects the sun gear 322 of theplanetary gear set 320 with the sun gear 332 of the planetary gear set330. A second interconnecting member 372 continuously connects the ringgear 324 of the planetary gear set 320 with the carrier 336 of theplanetary gear set 330, and with the ring gear 344 of the planetary gearset 340.

The transmission 314 also incorporates first and second motor/generators380 and 382, respectively. The stator of the first motor/generator 380is secured to the transmission housing 360. The rotor of the firstmotor/generator 380 is secured to the sun gear 322 of the planetary gearset 320. The stator of the second motor/generator 382 is also secured tothe transmission housing 360. The rotor of the second motor/generator382 is secured to the sun gear 342 of the planetary gear set 340.

A first torque-transfer device, such as the clutch 350, selectivelyconnects the sun gear 322 with the carrier 326. A second torque-transferdevice, such as the clutch 352, selectively connects the ring gear 334with the sun gear 342. A third torque-transfer device, such as brake354, selectively connects the ring gear 334 with the transmissionhousing 360. A fourth torque transfer device, such as the brake 355, isconnected in parallel with the motor/generator 380 for selectivelybraking rotation of the motor/generator 380. A fifth torque transferdevice, such as the brake 357, is connected in parallel with themotor/generator 382 for selectively braking rotation of themotor/generator 382. The first, second, third, fourth and fifthtorque-transfer devices 350, 352, 354, 355 and 357 are employed toassist in the selection of the operational modes of the transmission314.

The hybrid transmission 314 receives power from the engine 12, and alsoexchanges power with an electric power source 386, which is operablyconnected to a controller 388.

The operating mode table of FIG. 4 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 314. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 4 b. FIG. 4 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 4 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 320; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 330; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 340. Also, the chart of FIG. 4 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.89, the step ratio between the secondand third fixed forward torque ratios is 1.43, and the step ratiobetween the third and fourth fixed forward torque ratios is 1.89. Eachof the single step forward shifts between fixed ratios is a singletransition shift.

Description of a Fifth Exemplary Embodiment

With reference to FIG. 5 a, a powertrain 410 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral414. The transmission 414 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 414. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 414.An output member 19 of the transmission 414 is connected to a finaldrive 16.

The transmission 414 utilizes three planetary gear sets 420, 430 and440. The planetary gear set 420 employs an outer ring gear member 424which circumscribes an inner sun gear member 422. A carrier 426rotatably supports a plurality of planet gears 427 such that each planetgear 427 meshingly engages both the outer ring gear member 424 and theinner sun gear member 422 of the first planetary gear set 420.

The planetary gear set 430 also has an outer ring gear member 434 thatcircumscribes an inner sun gear member 432. A plurality of planet gears437 are also rotatably mounted in a carrier 436 such that each planetgear member 437 simultaneously, and meshingly engages both the outer,ring gear member 434 and the inner, sun gear member 432 of the planetarygear set 430.

The planetary gear set 440 also has an outer ring gear member 444 thatcircumscribes an inner sun gear member 442. A plurality of planet gears447 are also rotatably mounted in a carrier 446 such that each planetgear member 447 simultaneously, and meshingly, engages both the outerring gear member 444 and the inner sun gear member 442 of the planetarygear set 440.

The transmission input member 17 is continuously connected with thecarrier 426, and the transmission output member 19 is continuouslyconnected with the carrier 446. A first interconnecting member 470continuously connects the sun gear 422 with the sun gear 432. A secondinterconnecting member 472 continuously connects the ring gear 424 withthe carrier 436, and with the ring gear 444.

The transmission 414 also incorporates first and second motor/generators480 and 482, respectively. The stator of the first motor/generator 480is secured to the transmission housing 460. The rotor of the firstmotor/generator 480 is secured to the sun gear 422.

The stator of the second motor/generator 482 is also secured to thetransmission housing 460. The rotor of the second motor/generator 482 issecured to the sun gear 442.

A first torque-transfer device, such as a clutch 450, selectivelyconnects the sun gear 422 with the carrier 426. A second torque-transferdevice, such as clutch 452, selectively connects the ring gear 434 withthe carrier 446. A third torque-transfer device, such as brake 454,selectively connects the ring gear 434 with the transmission housing460. A fourth torque transfer device, such as the brake 455, isconnected in parallel with the motor/generator 480 for selectivelybraking rotation of the motor/generator 480. A fifth torque transferdevice, such as the brake 457, is connected in parallel with themotor/generator 482 for selectively braking rotation of themotor/generator 482. The first, second, third, fourth and fifthtorque-transfer devices 450, 452, 454, 455 and 457 are employed toassist in the selection of the operational modes of the transmission414. The hybrid transmission 414 receives power from the engine 12 andalso from an electric power source 486, which is operably connected to acontroller 488.

The operating mode table of FIG. 5 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 414. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

The transmission 414 is a dual mode transmission providing ratiosbetween 4.69 and 0.54.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 5 b. FIG. 5 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 5 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 420; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 430; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 440. Also, the chart of FIG. 5 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.89, the step ratio between the secondand third fixed forward torque ratios is 1.43, and the step ratiobetween the third and fourth fixed forward torque ratios is 2.21. Eachof the single step forward shifts between fixed ratios is a singletransition shift.

Description of a Sixth Exemplary Embodiment

With reference to FIG. 6 a, a powertrain 510 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral514. The transmission 514 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 514. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 514.An output member 19 of the transmission 514 is connected to a finaldrive 16.

The transmission 514 utilizes three planetary gear sets 520, 530 and540. The planetary gear set 520 employs an outer ring gear member 524which circumscribes an inner sun gear member 522. A carrier 526rotatably supports a plurality of planet gears 527 such that each planetgear 527 meshingly engages both the outer ring gear member 524 and theinner sun gear member 522 of the first planetary gear set 520.

The planetary gear set 530 also has an outer ring gear member 534 thatcircumscribes an inner sun gear member 532. A plurality of planet gears537 are also rotatably mounted in a carrier 536 such that each planetgear member 537 simultaneously, and meshingly engages both the outer,ring gear member 534 and the inner, sun gear member 532 of the planetarygear set 530.

The planetary gear set 540 also has an outer ring gear member 544 thatcircumscribes an inner sun gear member 542. A plurality of planet gears547 are also rotatably mounted in a carrier 546 such that each planetgear member 547 simultaneously, and meshingly, engages both the outerring gear member 544 and the inner sun gear member 542 of the planetarygear set 540.

The transmission input member 17 is continuously connected with thecarrier 526, and the transmission output member 19 is continuouslyconnected with the carrier 546. The first interconnecting member 570continuously connects the sun gear 522 with the sun gear 532. A secondinterconnecting member 572 continuously connects the ring gear 524 withthe carrier 536, and with the sun gear 542.

The transmission 514 also incorporates first and second motor/generators580 and 582, respectively. The stator of the first motor/generator 580is secured to the transmission housing 560. The rotor of the firstmotor/generator 580 is secured to the sun gear 522.

The stator of the second motor/generator 582 is also secured to thetransmission housing 560. The rotor of the second motor/generator 582 issecured to the ring gear 534.

A first torque-transfer device, such as a clutch 550, selectivelyconnects the ring gear 534 with the ring gear 544. A secondtorque-transfer device, such as a clutch 552, selectively connects thecarrier 536 with the ring gear 544. A third torque-transfer device, suchas a brake 554, selectively connects the ring gear 544 with thetransmission housing 560. A fourth torque transfer device, such as thebrake 555, is connected in parallel with the motor/generator 580 forselectively braking rotation of the motor/generator 580. A fifth torquetransfer device, such as the brake 557, is connected in parallel withthe motor/generator 582 for selectively braking rotation of themotor/generator 582. The first, second, third, fourth and fifthtorque-transfer devices 550, 552, 554, 555 and 557 are employed toassist in the selection of the operational modes of the hybridtransmission 514.

The hybrid transmission 514 receives power from the engine 12, and alsoexchanges power with an electric power source 586, which is operablyconnected to a controller 588.

The operating mode table of FIG. 6 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 514. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 6 b. FIG. 6 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 6 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 520; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 530; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 540. Also, the chart of FIG. 4 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.73 the step ratio between the secondand third fixed forward torque ratios is 1.69, and the step ratiobetween the third and fourth fixed forward torque ratios is 2.38. Eachof the single step forward shifts between fixed ratios is a singletransition shift.

Description of a Seventh Exemplary Embodiment

With reference to FIG. 7 a, a powertrain 610 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral614. The transmission 614 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 614. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 614.An output member 19 of the transmission 614 is connected to a finaldrive 16.

The transmission 614 utilizes three planetary gear sets 620, 630 and640. The planetary gear set 620 employs an outer ring gear member 624which circumscribes an inner sun gear member 622. A carrier 626rotatably supports a plurality of planet gears 627 such that each planetgear 627 meshingly engages both the outer ring gear member 624 and theinner sun gear member 622 of the first planetary gear set 620.

The planetary gear set 630 also has an outer ring gear member 634 thatcircumscribes an inner sun gear member 632. A plurality of planet gears637 are also rotatably mounted in a carrier 636 such that each planetgear member 637 simultaneously, and meshingly engages both the outer,ring gear member 634 and the inner, sun gear member 632 of the planetarygear set 630.

The planetary gear set 640 also has an outer ring gear member 644 thatcircumscribes an inner sun gear member 642. A plurality of planet gears647 are also rotatably mounted in a carrier 646 such that each planetgear member 647 simultaneously, and meshingly, engages both the outerring gear member 644 and the inner sun gear member 642 of the planetarygear set 640.

The transmission input member 17 is continuously connected with the ringgear 624, and the transmission output member 19 is continuouslyconnected with the carrier 646. A first interconnecting member 670continuously connects the carrier 626 with the carrier 636. A secondinterconnecting member 672 continuously connects the sun gear 622 withthe ring gear 634, and with the sun gear 642.

The transmission 614 also incorporates first and second motor/generators680 and 682, respectively. The stator of the first motor/generator 680is secured to the transmission housing 660. The rotor of the firstmotor/generator 680 is secured to the carrier 626.

The stator of the second motor/generator 682 is also secured with thetransmission housing 660. The rotor of the second motor/generator 682 issecured to the sun gear 632.

A first torque-transfer device, such as a clutch 650, selectivelyconnects the ring gear 624 with the carrier 626. A secondtorque-transfer device, such as a clutch 652, selectively connects thecarrier 646 with the ring gear 644. A third torque-transfer device, suchas a brake 654, selectively connects the ring gear 644 with thetransmission housing 660. A fourth torque transfer device, such as thebrake 655, is connected in parallel with the motor/generator 682 forselectively braking rotation of the motor/generator 682. The first,second, third and fourth torque-transfer devices 650, 652, 654 and 655are employed to assist in the selection of the operational modes of thehybrid transmission 614.

The hybrid transmission 614 receives power from the engine 12, and alsoexchanges power with an electric power source 686, which is operablyconnected to a controller 688.

The operating mode table of FIG. 7 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 614. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 7 b. FIG. 7 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 7 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 620; the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 630; and the N_(R3)/N_(S3) value is the toothratio of the planetary gear set 640. Also, the chart of FIG. 7 bdescribes the ratio steps that are attained utilizing the sample oftooth ratios given. For example, the step ratio between first and secondfixed forward torque ratios is 1.73, the step ratio between the secondand third fixed forward torque ratios is 1.69, and the step ratiobetween the third and fourth fixed forward torque ratios is 1.61.

Description of an Eighth Exemplary Embodiment

With reference to FIG. 8 a, a powertrain 710 is shown, including anengine 12 connected to one preferred embodiment of the improvedelectrically variable transmission, designated generally by the numeral714. The transmission 714 is designed to receive at least a portion ofits driving power from the engine 12.

As shown, the engine 12 has an output shaft that serves as the inputmember 17 of the transmission 714. A transient torque damper (not shown)may also be implemented between the engine 12 and the input member 17 ofthe transmission.

Irrespective of the means by which the engine 12 is connected to thetransmission input member 17, the transmission input member 17 isoperatively connected to a planetary gear set in the transmission 714.An output member 19 of the transmission 714 is connected to a finaldrive 16.

The transmission 714 utilizes three planetary gear sets 720, 730 and740. The planetary gear set 720 employs an outer ring gear member 724which circumscribes an inner sun gear member 722. A carrier 726rotatably supports a plurality of planet gears 727 such that each planetgear 727 meshingly engages both the outer ring gear member 724 and theinner sun gear member 722 of the first planetary gear set 720.

The planetary gear set 730 also has an outer ring gear member 734 thatcircumscribes an inner sun gear member 732. A plurality of planet gears737 are also rotatably mounted in a carrier 736 such that each planetgear member 737 simultaneously, and meshingly engages both the outer,ring gear member 734 and the inner, sun gear member 732 of the planetarygear set 730.

The planetary gear set 740 also has an outer ring gear member 744 thatcircumscribes an inner sun gear member 742. A plurality of planet gears747, 748 are also rotatably mounted in a carrier 746 such that eachplanet gear member 748 meshingly engages the outer, ring gear member744, and each planet gear member 747 meshingly engages the inner, sungear member 742 of the planetary gear set 740.

The transmission input member 17 is continuously connected with the ringgear 724, and the transmission output member 19 is continuouslyconnected with the ring gear 744. A first interconnecting member 770continuously connects the carrier 726 with the carrier 736. A secondinterconnecting member 772 continuously connects the sun gear 722 withthe ring gear 734 and with the sun gear 742.

The transmission 714 also incorporates first and second motor/generators780 and 782, respectively. The stator of the first motor/generator 780is secured to the transmission housing 760. The rotor of the firstmotor/generator 780 is secured to the carrier 726.

The stator of the second motor/generator 782 is also secured to thetransmission housing 760. The rotor of the second motor/generator 782 issecured to the sun gear 732.

A first torque-transfer device, such as a clutch 750, selectivelyconnects the ring gear 724 with the carrier 726. A secondtorque-transfer device, such as a clutch 752, selectively connects thecarrier 746 with the sun gear 732. A third torque-transfer device, suchas the brake 754, selectively connects the carrier 746 with thetransmission housing 760. A fourth torque transfer device, such as thebrake 755, is connected in parallel with the motor/generator 780 forselectively braking rotation of the motor/generator 780. A fifth torquetransfer device, such as the brake 757, is connected in parallel withthe motor/generator 782 for selectively braking rotation of themotor/generator 782. The first, second, third, fourth and fifthtorque-transfer devices 750, 752, 754, 755 and 757 are employed toassist in the selection of the operational modes of the hybridtransmission 714.

The hybrid transmission 714 receives power from the engine 12, and alsoexchanges power with an electric power source 786, which is operablyconnected to a controller 788.

The operating mode table of FIG. 8 b illustrates the clutchingengagements, motor/generator conditions and output/input ratios for thefive operating modes of the transmission 714. These modes include the“battery reverse mode” (Batt Rev), the “EVT reverse mode” (EVT Rev),“reverse and forward launch modes” (TC Rev and TC For), “continuouslyvariable transmission range modes” (Range 1.1, 1.2, 1.3 . . . ) and“fixed ratio modes” (F1, F2, F3, F4) as described previously.

As set forth above, the engagement schedule for the torque-transferdevices is shown in the operating mode table and fixed ratio mode tableof FIG. 8 b. FIG. 8 b also provides an example of torque ratios that areavailable utilizing the ring gear/sun gear tooth ratios given by way ofexample in FIG. 8 b. The N_(R1)/N_(S1) value is the tooth ratio of theplanetary gear set 720 and the N_(R2)/N_(S2) value is the tooth ratio ofthe planetary gear set 730. Also, the chart of FIG. 8 b describes theratio steps that are attained utilizing the sample of tooth ratiosgiven. For example, the step ratio between first and second fixedforward torque ratios is 1.73, the step ratio between the second andthird fixed forward torque ratios is 1.69, and the step ratio betweenthe third and fourth fixed forward torque ratios is 2.38.

In the claims, the language “continuously connected” or “continuouslyconnecting” refers to a direct connection or a proportionally gearedconnection, such as gearing to an offset axis.

While various preferred embodiments of the present invention aredisclosed, it is to be understood that the concepts of the presentinvention are susceptible to numerous changes apparent to one skilled inthe art. Therefore, the scope of the present invention is not to belimited to the details shown and described but is intended to includeall variations and modifications which come within the scope of theappended claims.

1. An electrically variable transmission comprising: an input member toreceive power from an engine; an output member; first and secondmotor/generators; first, second and third differential gear sets eachhaving first, second and third members; said input member beingcontinuously connected with at least one member of said gear sets, andsaid output member being continuously connected with another member ofsaid gear sets; a first interconnecting member continuously connectingsaid first member of said first gear set with said first member of saidsecond gear set; a second interconnecting member continuously connectingsaid second member of said first gear set with said second member ofsaid second gear set and with said second member of said third gear set;said first motor/generator being continuously connected with said firstinterconnecting member; said second motor/generator being continuouslyconnected with a member of said second or third gear set; a first torquetransfer device selectively connecting a member of said first or secondgear set with another member of said first or third gear set; a secondtorque transfer device selectively connecting a member of said thirdgear set with another member of said first, second or third gear set,the pair of members connected by said second torque transfer devicebeing different from the pair of members connected by said first torquetransfer device; and a third torque transfer device selectivelygrounding a member of said second or third gear set; a fourth torquetransfer device connected in parallel with one of said first and secondmotor/generators for selectively braking rotation thereof; wherein saidfirst, second, third and fourth torque transfer devices are engageablealone or in pairs to provide an electrically variable transmission witha continuously variable range of speed ratios and four fixed forwardspeed ratios.
 2. The electrically variable transmission of claim 1,wherein said first, second and third differential gear sets areplanetary gear sets.
 3. The electrically variable transmission of claim2, wherein carriers of each of said planetary gear sets aresingle-pinion carriers.
 4. The electrically variable transmission ofclaim 2, wherein at least one carrier of said planetary gear sets is adouble-pinion carrier.
 5. The electrically variable transmission ofclaim 1, further comprising a fifth torque transfer device, such as amotor brake, connected in parallel with the other of said first andsecond motor/generators for selectively braking rotation thereof.
 6. Theelectrically variable transmission of claim 1, wherein said first,second, third and fourth torque transfer devices and said first andsecond motor/generators are operable to provide five operating modes inthe electrically variable transmission, including battery reverse mode,EVT reverse mode, reverse and forward launch modes, continuouslyvariable transmission range mode, and fixed ratio mode.
 7. Anelectrically variable transmission comprising: an input member toreceive power from an engine; an output member; first and secondmotor/generators; first, second and third differential gear sets eachhaving first, second and third members; said input member beingcontinuously connected with at least one member of said gear sets, andsaid output member being continuously connected with another member ofsaid gear sets; a first interconnecting member continuously connectingsaid first member of said first gear set with said first member of saidsecond gear set; a second interconnecting member continuously connectingsaid second member of said first gear set with said second member ofsaid second gear set and with said second member of said third gear set;said first motor/generator being continuously connected with said firstinterconnecting member; said second motor/generator being continuouslyconnected with a member of said second or third gear set; and first,second, third and fourth torque transfer devices for selectivelyinterconnecting said members of said first, second or third gear setswith ground or with other members of said planetary gear sets, saidfirst, second, third and fourth torque transfer devices being engageablealone or in pairs to provide an electrically variable transmission witha continuously variable range of speed ratios and four fixed forwardspeed ratios between said input member and said output member.
 8. Theelectrically variable transmission of claim 7, wherein said first,second and third differential gear sets are planetary gear sets, andsaid first torque transfer device selectively connects a member of saidfirst or second planetary gear set with another member of said first orthird planetary gear set.
 9. The electrically variable transmission ofclaim 8, wherein said second torque transfer device selectively connectsa member of said third planetary gear set with another member of saidfirst, second or third planetary gear set, the pair of members connectedby said second torque transfer device being different from the pair ofmembers connected by said first torque transfer device.
 10. Theelectrically variable transmission of claim 9, wherein said third torquetransfer device selectively connects a member of said second or thirdplanetary gear set with a stationary member (ground).
 11. Theelectrically variable transmission of claim 10, wherein said fourthtorque transfer device is connected in parallel with one of said firstand second motor/generators for selectively braking rotation thereof.12. The electrically variable transmission of claim 11, wherein carriersof each of said planetary gear sets are single-pinion carriers.
 13. Theelectrically variable transmission of claim 11, wherein at least onecarrier of said planetary gear sets is a double-pinion carrier.
 14. Theelectrically variable transmission of claim 11, further comprising afifth torque transfer device, such as a motor brake, connected inparallel with the other of said first and second motor/generators forselectively braking rotation thereof.
 15. An electrically variabletransmission comprising: an input member to receive power from anengine; an output member; first and second motor/generators; first,second and third differential gear sets each having first, second andthird members; said input member being continuously connected with atleast one member of said gear sets, and said output member beingcontinuously connected with another member of said gear sets; a firstinterconnecting member continuously connecting said first member of saidfirst gear set with said first member of said second gear set; a secondinterconnecting member continuously connecting said second member ofsaid first gear set with said second member of said second gear set andwith said second member of said third gear set; said firstmotor/generator being continuously connected with said firstinterconnecting member; said second motor/generator being continuouslyconnected with a member of said second or third gear set; and first,second, third, fourth, and fifth torque transfer devices for selectivelyinterconnecting said members of said first, second or third gear setswith a stationary member or with other members of said planetary gearsets; wherein said first, second, third, fourth and fifth torquetransfer devices are engageable singly or in combinations of two toprovide an electrically variable transmission with a continuouslyvariable range of speed ratios and four fixed forward speed ratiosbetween said input member and said output member.